Alkali refining rice oil in the presence of a oh group-containing additive



- during refining operations, yield emulsions.

-oil entrained in these emulsions constitutes a second United States atent ALKALI REFINING RICE OIL IN THE PRESENCE OF A OH GROUP-CONTAINING ADDITIVE No Drawing. Application January 24, 1955 Serial No. 483,846

9 Claims. (Cl. 260-425) A non-exclusive irrevocable, royalty-free license in the invention herein described, for all governmental purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the alkali refining of crude natural glyceride oils, such as rice oil, which exhibit unusually high refining losses when refined by the usual alkali refining procedures.

The alkali refining of crude natural glyceride oils is a well established and long existing art. Basically the process comprises mixing the crude oil with aqueous alkali metal hydroxide and separating the mixture to obtain a refined oil and an oil insoluble mixture which contains fatty acid soaps and an aqueous solution or suspension of impurities which were present in the crude oil. The process is commercially carried out either continuously or batchwise, and numerous variations in the procedures and apparatus used to accomplish the basic steps are commonly employed. For example, in the .dry process, the proportions and mode of addition of the aqueous alkali metal hydroxide are adjusted to produce a relatively solid or dry soapstock, whereas in the wet process the soapstock is produced in the form of a rather free flowing aqueous slurry. In any case, the suitable procedures, apparatus, conditions of time, temperature and concentration of reactants, and the like, are well known to those skilled in the art. These are outlined in textbooks such as Industrial Oils and Fat Products, by A. E. Bailey, Interscience Publishers, Inc., 1945, and'the Oificial and Tentative Methods of the American Oil Chemists Society, and the like.

The alkali refining of a crude natural glyceride oil is always accompanied by a certain amount of lossof good ,oil due to saponification, entrainment in the soapstock,

and the like. In the case of rice oil and other hard to refine oils, these refining losses have heretofore been prohibitively high. For example, in the case of rice oil, refining losses of from 40 to 50%, or more, are common, regardless of free fatty acid content of the crude oil.

Refining losses in the caseof crude glyceride oils arise, in the main, from two sources. The two sources-of refining loss are interrelated to some degree but'not completely. An invariable requisite of conventional alkali refining (the specific type. of refining to which applicants processes are amenable) is the use of an excess of alkali over and above the stoichiometric amount required to neutralize thei actual amount of free fatty acid in the crude oil. The presence of excess alkali during the refining process inevitably leads to saponification of some neutral oil. This is one source of refining loss. Crude glyceride oils normally contain surface active agents. Lecithin is one example of such a surface active agent. Crude glyceride oils and their naturally occurring surface active agents when contacted with water, as happens The neutral "ice source of refining loss. Returning now'to'the'firstmen- 'tioned source of refining loss (saponification of neutral oil by excess alkali) it is obvi'ousthat thehigher thefree fatty acid content of the crude oil, "the greater willbe the amount'of alkali required for the refining and consequently the greater will be the lossof'neutral oil by reason of saponification. As a matter of fact,'the loss of neutral oil from this source :(saponifica'tion') is aggravated by the conventional refining practice of increasing 'the excess ofalkali dosage as the free fatty acid content of the crude'oil becomes, greater (see for'exa'mple the alkali dosage tables in AO CS Test Method Ca9a-S2). The loss of neutral oil by saponification augments loss from the second mentioned source (entrainment-of 'neutral oil in water-oil emulsions that result from the presence of naturally occurring surface active'a'gents 'in the crude oil) since a product of alkali neutralization'of free fatty acid and saponification of neutral oil is so'ap which of itself is a surface active agent.

The term hard to refine is used herein to designate crude natural glyceride oils which, for one reason or another, exhibit an unusually high refining loss typical of the ordinary crude rice oils when they are refined by an alkali refining procedure, such as, the America'nOil Chemists Society Test Method for Hydraulic Cottonseed Gil Ca9a-52 (a test that is commonly used in the art to assist in determining the market value of a crude natural glyceride oil). In general, the crude naturalglyceride oils other than rice oil which are hard to refine oils are characterized by a free fatty acid content 'of more than about 2% and the exhibition of a refiningloss of more than about .four times the free fatty acid content when they are refined by the AOCS Test Method -Ca'9a-5 2.

A primary object of the present invention is to provide an improved process of alkali refining the hard to refine crude natural glyceride oils.

In accordance with the present invention; when such oils are alkali refined in the presence of a small amount of the additive defined below, the refining process results in a good quality refined oil having a low free fatty acid content. The soapstocks formed in the presence of the additive are usually firm Whereas those formed in the absence of the additive are sof and the refining loss in the presence of the additive is usually materially smaller than that in the absence of the additive. These improvements are obtained when the alkali refining is conducted in the presence of the additive either as a con tinuous or batch process using any of the usual procedures or apparatus usually employed in the wet or dry alkali refining of crude natural glyceride oiE. Unobviously, however, these improvements appear to be unique to the alkali refining of the hard to refine oils. When a crude natural glyceride oil having normal refining properties is alkali refined in the-presence of the additive, the refining loss is usually higher than that exhibited in the absence of the additive; and the soapstock is usually less firm than the soapstock produced in the absence of the additive.

In general, in accordance with this invention a hard to refine crude natural glyceride oil is alkali refined with a reduced refining loss by alkali refining the oil in the presence of an effective amount of an additive consisting of at least one compound which is soluble in the oil or the aqueous alkali and contains at least two OH groups each of which is attached to a saturated carbon atom which is attached only to carbon and hydrogen atoms.

Our copending applications Serial Nos.'483,844 and 483,845, filed of even date, relate to similar processes employing additives consisting of ethylol derivatives of ammonia and additives consisting of NH-group-containing compounds, respectively.

Illustrative examples of hard to refine oils to which this invention is applicable include the usual crude rice oils, and those of the crude natural glyceride oils (or, fats) extracted from vegetable or animal oil bearing materials such as cottonseed, peanuts, soybeans, animals, or fishes which contain more than about 2% free fatty acid and exhibit a refining loss of more than about four times their free fatty acid content when refined by the solutions such as sorgo juice, blackstrap molasses, and

the like; polyhydroxy ketones, such as, methyl 3,4-dihydroxypentyl ketone, and the like; polyhydroxy aldehydes,

such as, alpha,gamma-dihydroxycaproic aldehyde and the like; and'polyhydroxy acids, such as, glyceric acid, 3,12-dihydroxypalmitic acid, 9,10-dihydroxystearic acid and the like. The sugars and the 2 to 5 carbon atom poly- .hydric aliphatic alcohols are particularly suitable for employment in the practice of this invention.

The amount of additive usedcan be varied widely, depending upon the particular oil being refined and the amount of reduction in refining loss desired. The amount by which the refining loss exhibited by a given oil is reduced bythe presence of the adidtive usually increases as the amount of additive is increased, until a readily determinable' optimum proportion is reached. In general,

7 the use of from about 0.5 to 5% of the weight of the oil is suitable. However, in any case, the proportion of additive which provides an effective amount can readily be determined by test refinings, in accordance with the AOCS Test Method Ca9a-52, in the presence of various proportions of additive. In the case of hard to refine oils containing unusually high proportions of free fatty acids (e. g. more than about 10.0%) it is often economically advantageous to distill olf enough of the acids to provide a free fatty acid content of from about 2 to 10.0%, prior to refining the oils.

The process of this invention is particularly adapted to the refining of crude rice oil. In general, in the refining of a crude rice oil, it is preferable to mix from about 1 to 3% of at least one additive such as a sugar or a 2 to 5 carbon atom polyhydric aliphatic alcohol with the oil,

just prior to mixing the oil with the aqueous alkali metal hydroxide.

The following examples are illustrative of the details of at least one method of practicing this invention.

EXAMPLE 1 I Comparative refinings of rice oil in the presence of various additives The oil used was a crude clarified rice oil having a free fatty acid content of 6.6%.

In each case, the oil was refined by mixing it with the indicated amount of additive (in percent by weight of the oil) and refining the mixture by the AOCS Test Method Ca9a-52, modified in that: 100 gram samples of the oil in 250 ml. beakers were used; a smaller but substantially equivalent agitator was. used at substantially equivalent cold and hot stirring speeds; and the yields of refined oil were determined shortly: after the samples had cooled to room temperature. 7

The refimngs resulted in the indicated refimng losses.

Amount Additive Added, Refining Wt. Per- Loss cent Control (i. e., without additive) 44. 1 Ethylene glycol 1. 9 19. 4 Glycerol 2. 6 20. 6 Propylene glycol 2. 2 22. 4 Trimethylene glycol 2. 2 23. 2 Sucr P 3.0 19.4 Blackstrap molasses 2. 5 23. 3

EXAMPLE 2 Normal and hard to refine cottonseed oils The oils used were: (A) an ordinary crude hydraulic cottonseed oil having a free fatty acid content of 0.6% and (B) a hard to refine crude hydraulic cottonseed oil having a free fatty acid content of 2.0%. Oil A is one which would be classified as easy to refine when refined according to AOCS Test Method Ca9a52.

The refining losses exhibited when the oils were refined in the presence and absence of sucrose in accordance with the procedure described in Example 1 were:

Refining Refining Sample Loss with Loss with- Additive out Addi- (3.0%) tive A (FFA=O.6%) 5. 7 4. 2 B (FFA=2.0%) l3. 5 I 27. 8

As will be apparent to those skilled in the art, the process of this invention materially improves the refining (on the basis of refining loss) of the hard to refine cottonseed oil; but adversely affects the refining of an ordinary cottonseed oil. This unobvious result is confirmed by the character of the soapstocks obtained: those from the ordinary oil, A, were firm in the absence of the additive, and were soft in the presence of the additive; whereas, in the case of the hard to refine oil, B, the soapstocks were firm in the presence of the additive, and were soft in the absence of the additive.

We claim:

1. A process of alkali refining, with a comparatively low refining loss, a hard to refine crude natural glyceride oil selected from the group consisting of crude rice oil, cottonseed oil, peanut oil, soybean oil, animal fats, and fish oils, which oil exhibits a refining loss that is more than about four times the free fatty acid content of the crude oil when refined by the AOCS Test Method Ca9a-52, which comprises alkali refining the oil by the AOCS Test Method Ca9a-52 in the presence of about from 0.5 to 5 weight percent based on the weight of crude oil of at least one OH group-containing compound selected from the group consisting of sugars and 2 to 5 carbon atom polyhydric aliphatic alcohols.

2. The process of claim 1 in which the OH groupcontaining compound is blackstrap molasses.

3. The process of claim 1 in which the OH groupcontaining compound is sucrose.

4. The process of claim 1 in which the OH groupcontaining compound is ethylene glycol.

5. The process of claim 1 in which the OH groupcontaining compound is glycerol.

6. A process of alkali refining, with a comparatively low refining loss, a hard to refine crude cottonseed oil which exhibits a refining loss of more than about four times the free fatty acid content when refined by the AOCS Test Method Ca9a-52 which comprises alkali refining the crude cottonseed oil by the AOCS Test Method Ca9a-52 in the presence of about from 0.5 to 5 weight percent based on the weight of the crude oil of at least one OH group-containing compound selected from the group consisting of sugars and 2 to 5 carbon atom polyhydric aliphatic alcohols.

7. The process of claim 6 in which the OH groupcontaining additive is sucrose.

8. A process of alkali refining a crude rice oil, with a comparatively low refining loss, which comprises alkali refining the oil by the AOCS Test Method Ca9a-52 in the presence of about from 0.5 to 5 weight percent based on the weight of crude oil of at least one -OH group-containing compound selected from the group consisting of sugars and 2 to 5 carbon atom polyhydric aliphatic alcohols.

9. A process of alkali refining, with a comparatively.

oil which exhibits a refining loss of more than about four times the free fatty acid content when refined by the AOCS Test Method Ca9a-52, which comprises alkali refining the oil by the AOCS Test Method Ca9a-52 in the presence of about from 0.5 to 5 weight percent based on the weight of the crude oil of at least one -OH groupcontaining compound selected from the group consisting of sugars and 2 to 5 carbon atom polyhydric aliphatic alcohols.

References Cited in the file of this patent UNITED STATES PATENTS 

9. A PROCESS OF ALKALI REFINING, WITH A COMPARATIVELY LOW REFINING LOSS, A HARD TO REFINE CRUDE NATURAL GLYCERIDE OIL WHICH EXHIBITS A REFINING LOSS OF MORE THAN ABOUT FOUR TIMES THE FREE FATTY ACID CONTENT WHEN REFINED BY THE AOCS TEST METHOD CA9A-52, WHICH COMPRISES ALKALI REFINING THE OIL BY THE AOCS TEST METHOD CA9A-52 IN THE PRESENCE OF ABOUT FROM 0.5 TO 5 WEIGHT PERCENT BASED ON THE WEIGHT OF THE CRUDE OIL OF AT LEAST ONE -OH GROUPCONTAINING COMPOUND SELECTED FROM THE GROUP CONSISTING OF SUGARS AND 2 TO 5 CARBON ATOM POLYHYDRIC ALIPHATIC ALCOHOLS. 